Oculopression is the process of applying pressure to the external surface of the eye, for the purpose of reducing intraocular pressure (IOP). The eye contains structures for the self-regulation of IOP, such that a period of compression will lead to a lower than normal IOP upon release.
Prior to significant surgery of the eye (eg penetrating keratoplasty, internal procedures etc), an anaesthetic agent is injected behind the eye, in the rear of the socket. This retrobulbar or peribulbar “block” administers an amount of fluid behind the eye to anaesthetise the optic nerve and surrounding region. The administration of fluid behind the eye causes the IOP to increase and fluid to accumulate under the conjunctiva. This effect is called Chemosis and is generally obstructive for surgery.
Oculopression in this circumstance serves to both assist the dispersal of fluid and the reduction in IOP, which are advantageous for penetrating surgery.
Oculopression may be achieved through digital application of force by the practitioner, however, manual application introduces variance in pressure and location which may reduce the effectiveness of the procedure, plus the mobility of the practitioner is restricted for this period.
It is known that application of excessive force or application for excessive duration may damage the eye structure or restrict ocular circulation, which may lead to blindness or loss of the eye. This condition is known as ischemia and is caused by local restriction of blood vessels and subsequent metabolic compromise. Damage caused by ischemia may be temporary or permanent, depending on the degree of cellular damage. An accepted appropriate pressure to be applied is approximately 30 mm of mercury, for a maximum constant duration of about 15 minutes. Between applications of pressure, the eye should be “rested” to enable circulation to normalise. This period may be as little as a few minutes, and the program of safe oculopression is commonly monitored according to the patient condition by an appropriately skilled practitioner. In order to reduce risks of ischemia, it is considered advantageous that the duration of oculopression should be brought to the attention of the practitioner for action within the recommended duration. Existing devices do not address this issue.
Further disadvantages of existing devices arise from the form of the device and the location to the eye. The internal pressure-regulating structures of the eye rely on gradual diffusion of fluid, and the external eye tissues may display a memory-type effect to deformation, as the application of force to the eye surface via a connecting structure of non-conforming or small surface area may lead to short-term reshaping of the eye which is disadvantageous for some surgery.
Thus, an opportunity exists to apply a safety feature to an oculopression device which indicates the duration of application of the pressure, whilst maintaining the correct disposition of the eye for subsequent surgery.
Oculopression devices using the action of gravity on a mass are known. Alternate methods include expandable air-filled balloons affixed against the patient's eye (U.S. Pat. No. 4,175,562), goggles, cuffs and the like, most using air pressure to alter the pressure in a chamber in contact with the eye (U.S. Pat. No. 4,387,707 and European Patent No. EP0841047).
None of these devices in their various forms relate to indication or control of the duration of application of force as a means of reducing ischemic risks.